Stockholders' Equity (Common Stock) (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2017	Feb. 03, 2018	Jan. 28, 2017	Jan. 30, 2016	Mar. 31, 2018	Feb. 28, 2018
Class of Stock [Line Items]
Stock repurchased program period	2 years
Stock repurchase program, approved amount	$ 1,750,000,000
Shares repurchased (in shares)		13.5	11.6	13.7
Average repurchase price (in dollars per share)		$ 64.87	$ 60.15	$ 51.27
Common stock repurchased, value		$ 875,000,000	$ 700,000,000	$ 700,000,000
Subsequent Event
Class of Stock [Line Items]
Stock repurchase program, authorized increase					$ 200,000,000
Stock repurchase program, remaining amount					$ 1,075,000,000	$ 875,000,000